Adenoviruses — a group of viruses that infect the membranes (tissue linings) of the respiratory tract, the eyes, the intestines, and the urinary tract — account for about 10% of acute respiratory infections in children and are a frequent cause of diarrhea.

Adenoviral infections affect infants and young children much more frequently than adults. Child-care centers and schools sometimes experience multiple cases of respiratory infections and diarrhea that are caused by adenovirus.

Although these infections can occur at any time of the year, respiratory tract disease caused by adenovirus is more common in late winter, spring, and early summer. However, conjunctivitis and pharyngoconjunctival fever caused by adenovirus tend to affect older kids mostly in the summer.

The majority of the population will have experienced at least one adenoviral infection by age 10. Although adenoviral infection in kids can occur at any age, most take place in the first years of life. Since there are many different types of adenovirus, repeated adenoviral infections can occur.

Signs and Symptoms

Depending on which part of the body is affected, the signs and symptoms of adenoviral infections vary:

Febrile respiratory disease, which is an infection of the respiratory tract that includes a fever, is the most common result of adenoviral infection in children. The illness often appears flu-like and can include symptoms of pharyngitis (inflammation of the pharynx, or sore throat), rhinitis (inflammation of nasal membranes, or a congested, runny nose), cough, and swollen lymph nodes (glands). Sometimes the respiratory infection leads to acute otitis media, an infection of the middle ear. Adenovirus often affects the lower respiratory tract as well, causing bronchiolitis, croup, or viral pneumonia, which is less common but can cause serious illness in infants. Adenovirus can also produce a dry, harsh cough that can resemble whooping cough (pertussis).

Gastroenteritis is an inflammation of the stomach and the small and large intestines. Symptoms include watery diarrhea, vomiting, headache, fever, and abdominal cramps.

Conjunctivitis (or pinkeye) is a mild inflammation of the conjunctiva (membranes that cover the eye and inner surfaces of the eyelids). Symptoms include red eyes, discharge, tearing, and the feeling that there's something in the eye.

Pharyngoconjunctival fever, often seen in small outbreaks among school-age children, occurs when adenovirus affects both the lining of the eye and the respiratory tract. Symptoms include very red eyes and a severe sore throat, sometimes accompanied by low-grade fever, rhinitis, and swollen lymph nodes.

Keratoconjunctivitis is a more severe infection that involves both the conjunctiva and cornea (the transparent front part of the eye). This type of adenoviral infection is extremely contagious, and occurs most often in older children and young adults, who complain of red eyes, photophobia (discomfort of the eyes upon exposure to light), tearing, and pain.

Contagiousness

Adenovirus is highly contagious, as indicated by the occurrence of multiple cases in situations of close contact, such as child-care centers, schools, hospitals, and summer camps.

The types of adenovirus that cause respiratory and intestinal infections spread from person to person through respiratory secretions (coughs or sneezes) or fecal contamination. Fecal material can be ingested through contamination of water supplies, poor hand washing between the bathroom and the kitchen, eating food contaminated by houseflies, or poor hygiene after handling diapers.

A child might also pick up the virus by holding hands or sharing a toy with an infected person. Indirect transmission can occur through exposure to the contaminated surfaces of furniture and other objects.

The types of adenovirus causing conjunctivitis may be transmitted by water (in lakes and swimming pools), by sharing contaminated objects (such as towels or toys), or by touch.

Once a child is exposed to adenovirus, symptoms can develop from 2 days to 2 weeks later.

Treatment

Adenoviral illnesses often resemble certain bacterial infections, which can be treated with antibiotics. But antibiotics don't work against viruses. To diagnose the true cause of the symptoms so that proper treatment can be prescribed, your doctor may want to test a sample of respiratory or conjunctival secretions, a stool specimen, or blood or urine sample — depending on what condition is being considered.

The doctor will decide on a course of action based on your child's condition. Adenoviral infections usually don't require hospitalization. However, infants and young children may not be able to drink enough fluids to replace what they lose during vomiting or diarrhea and may therefore need to be hospitalized to correct or prevent dehydration. Also, young — especially premature — infants with pneumonia usually need to be hospitalized.

In most cases, a child's body will get rid of the virus over time. Because antibiotics are of no use in treating a viral infection, you should simply try to make your child more comfortable.

If your child has a respiratory infection or fever, getting plenty of rest and taking in extra fluids is essential. A cool-mist humidifier (vaporizer) may help loosen congestion and make your child more comfortable. Be sure to clean and dry the humidifier thoroughly each day to prevent bacterial or mold contamination. If your child is under 6 months old, you may need to clear his or her nose with a bulb syringe.

Don't give any over-the-counter (OTC) cold remedies or cough medicines without checking with your child's doctor. You can use acetaminophen to treat a fever; however, do not give aspirin because of the risk of Reye syndrome, a life-threatening illness.

If your child has diarrhea or is vomiting, increase fluid intake and check with the doctor about giving an oral rehydration solution to prevent dehydration.

To relieve the symptoms of conjunctivitis, use warm compresses and a topical eye ointment or drops if your doctor recommends them.

Duration

Most adenoviral infections last from a few days to a week. Severe respiratory infections may last longer and cause lingering symptoms, such as a cough. Pneumonia can last anywhere from 2 to 4 weeks.

In cases of pharyngoconjunctival fever, sore throat and fever may disappear within a week, but conjunctivitis can persist for another several days to a week. The more severe keratoconjunctivitis can even last for several weeks. Adenovirus can also cause diarrhea that lasts up to 2 weeks, which is longer than other viral diarrheas.

Prevention

There's no way to completely prevent adenoviral infections in kids. To reduce the risk of transmission, parents and other caregivers should encourage frequent hand washing, keep shared surfaces such as countertops and toys clean, and remove children with infections from group settings until symptoms subside.

When to Call the Doctor

Most of these adenoviral conditions and their symptoms are also associated with other causes. Call your doctor if:

a fever continues more than a few days

symptoms seem to get worse after a week

your child has breathing problems

your child is under 3 months old

any swelling and redness around the eye becomes more severe or painful

your child shows signs of dehydration, such as appearing tired or lacking energy, producing less urine or tears, or having a dry mouth or sunken eyes

Remember that you know your child best. If he or she appears to be severely ill, don't hesitate to call your doctor right away.